UPSC Prelims Current Affairs for 13 September 2026

by Vajiram & Ravi - 13 September 2026

Vajiram & Ravi provides Daily UPSC Prelims Current Affairs for 13 September 2026, tailored for aspirants. We cover all relevant news and events crucial for the exam, ensuring you stay updated & well-prepared.

Deltachion ravenshaw

September 13, 2026
What is Deltachion ravenshaw

Deltachion ravenshaw Latest News

Researchers recently identified a previously undescribed species named  Deltachion ravenshaw from the sandy intertidal stretches of the Devi estuary in Puri.

About Deltachion ravenshaw

  • It is a new clam species.
  • It belongs to Donacidae, a family of bivalve molluscs of the order Veneroida.   
  • It was discovered from the sandy intertidal stretches of the Devi estuary in Puri, Odisha.
  • According to the study, 12 Donacidae species are currently recorded in India, seven of them from the Odisha coast.
  • What makes the discovery particularly interesting is the place where the bivalve was found. 
  • Deltachion species are generally associated with marine environments, while D. ravenshaw was found in the brackish waters of the Devi estuary, where salinity can fluctuate. 
  • Measuring about 6.9 mm, the bivalve has an elongated, triangular shell with a distinctly pointed anterior end.
  • Its posterior portion has prominent, broad, and flat radial ribs, with fine intersecting lines creating a characteristic lattice-like pattern.
  • Differences in these shell features, along with the shape of its pallial sinus and ventral margin, help distinguish it from closely related species.

News: TOI

Deltachion ravenshaw FAQs

Q1: What is Deltachion ravenshaw?

Ans: It is a new species of clam.

Q2: From which location was Deltachion ravenshaw discovered?

Ans: The sandy intertidal stretches of the Devi estuary in Puri, Odisha.

Q3: What is unusual about the habitat of Deltachion ravenshaw?

Ans: It was found in the brackish waters of the Devi estuary, despite Deltachion species generally being associated with marine environments.

Q4: What is the characteristic shape of the shell of Deltachion ravenshaw?

Ans: An elongated, triangular shell with a distinctly pointed anterior end.

Fermat’s Last Theorem

September 13, 2026
What is Fermat’s Last Theorem

Fermat’s Last Theorem Latest News

Anthropic recently used its Claude AI to formalise Fermat’s Last Theorem using the Lean language.

About Fermat’s Last Theorem

  • It is a famous mathematical statement proposed by Pierre de Fermat in 1637 claiming that the equation x^n + y^n = z^n has no integer solutions for n > 2.
  • This conjecture was noted in the margin of Fermat's copy of "Arithmetica," an ancient Greek text on number theory, where he famously stated that he had a proof too large to fit in the margin. 
  • While solutions exist for n = 1 and n = 2 (known as linear and Pythagorean equations, respectively), the case for (n > 2) remained unsolved for over 350 years, making it one of the most significant unsolved problems in mathematics. 
  • The eventual proof was provided by mathematician Andrew Wiles in 1995, utilizing concepts from the modularity theorem for elliptic curves. 
  • Wiles's work built on earlier contributions from mathematicians like Gerhard Frey and Ken Ribet, who connected concepts related to elliptic curves and Fermat's conjecture.  
  • The theorem has not only resolved a long-standing mystery in mathematics but has also spurred advancements in areas such as algebraic number theory and the study of Diophantine equations.

News: TH

Fermat’s Last Theorem FAQs

Q1: Who proposed Fermat’s Last Theorem?

Ans: Pierre de Fermat.

Q2: What does Fermat’s Last Theorem state?

Ans: The equation x^n + y^n = z^n has no positive integer solutions for n>2.

Q3: Where did Pierre de Fermat write his famous note about the theorem?

Ans: In the margin of his copy of Arithmetica.

Q4: Who provided the proof of Fermat’s Last Theorem?

Ans: Andrew Wiles.

Q5: Which mathematical concept played a crucial role in Andrew Wiles’s proof of Fermat’s Last Theorem?

Ans: The modularity theorem for elliptic curves.

Hasdeo River

September 13, 2026
Key Facts about Hasdeo River

Hasdeo River Latest News

One student drowned, and two others were recently swept away in the Hasdeo River while they were on a picnic in Chhattisgarh’s Janjgir-Champa district.

About Hasdeo River

  • It is a major tributary of the Mahanadi River. 
  • It flows through Chhattisgarh state.
  • Course:
    • It originates from a small lake near the Ambikapur town of Surguja district in Chhattisgarh. 
    • The river flows through Surguja, Korea, and Bilaspur districts and empties into the Mahanadi River near Akaltara in Janjgir–Champa district. 
  • Its course is about 333.0 km long. The river flows through lush green forests, deep valleys, hills, and many small villages. 
  • The Hasdeo basin includes the ecologically important Hasdeo Arand forest region, considered the largest unfragmented forest landscape in Central India. 
  • Hasdeo Bango Dam: The Hasdeo Bango Reservoir is constructed across the river  that plays a vital role in irrigation and hydroelectric power generation. 
  • Important Tributaries: Gej and Ahiran

News: TP

Hasdeo River FAQs

Q1: Which major river is the Hasdeo River a tributary of?

Ans: The Mahanadi River.

Q2: In which state does the Hasdeo River flow?

Ans: Chhattisgarh.

Q3: Where does the Hasdeo River originate?

Ans: From a small lake near Ambikapur in Surguja district, Chhattisgarh.

Q4: What is the approximate length of the Hasdeo River?

Ans: About 333 km.

Q5: Which are the important tributaries of the Hasdeo River?

Ans: Gej and Ahiran.

Mayun Island

September 13, 2026
Key Facts about Mayun Island

Mayun Island Latest News

Yemen’s Iranian-backed Houthi rebels recently captured the strategic island of Mayun in the Bab el-Mandeb Strait at the entrance to the Red Sea.

About Mayun Island

  • Mayun Island, also known as Perim Island, is a small volcanic island belonging to Yemen, located in the strategically important Bab el-Mandeb Strait, at the southern entrance to the Red Sea. 
  • Although rocky and just 13 sq.km. in area, the volcanic island rises as high as 65 m and overlooks the strait near its narrowest point, about 26 km wide. 
  • Perim Island actually splits the Bab el-Mandeb Strait into two smaller channels. 
  • The importance of the small island grew with the advent of the Suez Canal, which connected the Mediterranean Sea and the Arabian Sea through the Red Sea and allowed global shipping routes to bypass the lengthy route around Africa.  
  • As steps were taken to begin the construction of the canal, the British seized the island in 1857 and established a coaling station, which later went bankrupt in 1935. 
  • For many years, from 1857 to 1967, Perim Island was part of the British Empire. 
  • Perim Island became part of independent Yemen (Aden) in 1967. 
  • The Bab el-Mandeb Strait became a vital chokepoint along the new route, and Perim Island’s position within the strait gave its occupier command over the eastern channel and a measure of control over its western channel. 
  • It has a deep and large natural harbor on its southwestern side and a military airfield in the north.

News: NOA

Mayun Island FAQs

Q1: What is another name for Mayun Island?

Ans: Perim Island.

Q2: Which country does Mayun Island belong to?

Ans: Yemen.

Q3: In which strait is Mayun Island located?

Ans: The Bab el-Mandeb Strait.

Q4: Where is Mayun Island located in relation to the Red Sea?

Ans: At the southern entrance to the Red Sea.

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